We will investigate the sequence diversity and mutational mechanisms that underlie the high frequency of mutations found in forest trees for specific genes in the lignin biosynthetic pathway. Specifically, we will" Obtain nucleotide diversity estimates for several specific lignin biosynthetic genes. Establish gene family structure and allelic relationships Determine the frequency of loss-of-function mutations and functional variants. Characterize activity of functional variants in bacterial or yeast expression systems. Investigate the relationship of repeated sequence elements and loss-of-function mutations by screening for new mutations and characterizing their sequences. Three gene families in the lignin biosynthetic pathway are of particular interest for detailed sequence analysis: the CAD gene family, the CCR gene family, and the PAL gene family. Characterize loss-of-function mutations using cDNA microarrays to identify the extent of specific changes in gene expression due to epistatic interactions. Test for association of DNA sequence variation with lignin phenotypic variation.